Credential Harvesting

Credential harvesting is how attackers collect usernames and passwords at scale. It’s the starting point for most account takeovers, data breaches, and ransomware attacks.

According to the SpyCloud Identity Threat Report 2025, 91% of organizations experienced an identity-related security incident in the past year. Most of those incidents trace back to harvested credentials.

Understanding how credential harvesting works helps security teams detect exposures early and prevent the attacks that follow.

What Is Credential Harvesting?

Credential harvesting is a cyberattack technique where attackers collect user login credentials through deceptive or malicious means. Unlike brute force attacks that guess passwords, credential harvesting captures real credentials that victims enter themselves or that malware extracts from their systems.

The harvested credentials typically end up in one of three places: sold on dark web marketplaces, aggregated into combo lists for automated attacks, or used directly for targeted account takeovers.

What makes credential harvesting dangerous is scale. A single phishing campaign can harvest thousands of credentials in hours. Infostealer malware running on one infected device can capture every password saved in the browser. When attackers combine these techniques with automation, they amass credentials that fuel credential stuffing attacks.

How Does Credential Harvesting Work?

Credential harvesting follows a predictable pattern regardless of the specific technique used.

Target identification. Attackers select their victims based on value. Corporate employees with access to sensitive systems are high-priority targets. So are users of financial services, healthcare portals, and cloud platforms. Some attackers cast wide nets; others focus on specific organizations.

Credential capture. The attacker deploys their harvesting method: a phishing page that mimics a legitimate login, malware that monitors keystrokes, or a man-in-the-middle proxy that intercepts authentication. The victim enters credentials thinking they’re logging into a real service.

Data exfiltration. Captured credentials get sent to attacker-controlled infrastructure. Phishing kits automatically log every submission. Infostealer malware uploads harvested data to command-and-control servers. The credentials are now in the attacker’s hands.

Monetization or exploitation. Attackers either use the credentials themselves or sell them. High-value corporate credentials command premium prices on criminal forums. Consumer credentials get aggregated into bulk lists sold for cents per record.

What Are the Main Types of Credential Harvesting Attacks?

Security teams should understand the most common harvesting techniques to build effective defenses.

Phishing Attacks

Phishing remains the top credential harvesting method. Attackers create convincing replicas of login pages for Microsoft 365, Google Workspace, banking portals, and corporate VPNs. They distribute links through email, SMS, or social media.

Modern phishing kits are turnkey operations. They include pre-built templates for dozens of services, automatic credential logging, and even real-time relay capabilities that capture MFA tokens. The IBM Cost of a Data Breach Report 2025 found phishing was the number one initial attack vector, accounting for 16% of breaches.

Infostealer Malware

Infostealer malware has industrialized credential theft. Families like RedLine, Vidar, and Raccoon run silently on infected devices, extracting saved passwords from browsers, capturing form submissions, and stealing session cookies.

What makes infostealers particularly dangerous is their comprehensiveness. A single infection can harvest credentials for every service the victim uses. The malware also captures session tokens that bypass MFA entirely. According to the SpyCloud 2025 report, nearly half of corporate users have been infected with infostealer malware at some point.

Man-in-the-Middle Attacks

Attackers position themselves between users and legitimate services to intercept credentials in transit. Reverse proxy phishing kits sit between victims and real login pages, capturing credentials and session tokens in real-time.

These attacks are especially effective against MFA because they capture the complete authentication session, including one-time codes and session tokens.

Credential Dumping

Once attackers gain access to a system, they extract credentials stored locally. Tools like Mimikatz pull passwords and hashes from Windows memory. Attackers dump credentials from LSASS processes, registry hives, and cached domain credentials.

Credential dumping enables lateral movement. An attacker who compromises one workstation can harvest credentials that provide access to servers and domain controllers.

Keyloggers

Keyloggers capture every keystroke on an infected device, recording usernames and passwords as users type them. They often bundle with other malware or come as standalone infections.

Why Is Credential Harvesting Dangerous?

Harvested credentials enable a cascade of attacks that extend far beyond the initial theft.

Direct financial impact. The IBM 2025 report found breaches involving compromised credentials cost organizations an average of $4.67 million. These breaches also take longer to detect and contain, extending attacker dwell time.

Account takeover. With valid credentials, attackers log in as legitimate users. They access email, cloud storage, financial accounts, and corporate systems without triggering alerts. Traditional security tools can’t distinguish between a real user and an attacker using stolen credentials.

Credential reuse amplifies damage. When people reuse passwords across services, one harvested credential unlocks multiple accounts. Attackers test stolen credentials against dozens of services automatically. A password harvested from a gaming forum might work on the victim’s corporate VPN.

Lateral movement. In corporate environments, harvested credentials provide footholds for deeper compromise. Attackers move from user workstations to servers, from employee accounts to admin credentials, from one system to the entire network.

How Do You Detect Credential Harvesting?

Detection happens at two levels: catching attacks in progress and finding exposed credentials before attackers use them.

Monitor for phishing indicators. Email security tools flag suspicious messages with links to newly registered domains or known phishing infrastructure. User reports of unusual login prompts or password reset requests signal active campaigns.

Watch for infostealer infections. Endpoint detection tools can identify infostealer malware execution. But many infections happen on personal devices outside corporate visibility. This is where dark web monitoring becomes critical.

Check the dark web for exposed credentials. Credential monitoring platforms scan the same sources attackers use: dark web marketplaces and stealer log channels. When your organization’s credentials appear, you can reset them before attackers exploit them.

Detect authentication anomalies. Impossible travel, unusual login times, and access from new devices can indicate compromised credentials in use. User behavior analytics spots when attackers are using stolen credentials.

How Do You Prevent Credential Harvesting?

Prevention requires layering technical controls with user education.

Deploy phishing-resistant MFA. Hardware security keys and FIDO2 authentication prevent phishing-based credential harvesting because there’s no password to steal. They don’t protect against infostealer malware that captures session tokens after you authenticate.

Use password managers. When employees use unique passwords for every service, credential harvesting from one breach doesn’t cascade to other accounts. A password manager lets your team use unique passwords everywhere without memorizing them.

Implement email security controls. Advanced email filtering blocks most phishing attempts before they reach users. URL rewriting and sandboxing provide additional protection against malicious links.

Train users to recognize phishing. Simulated phishing campaigns build awareness and help identify users who need additional training. The goal isn’t perfection but raising the bar high enough that attackers look for easier targets.

Monitor for exposed credentials continuously. Dark web monitoring detects when harvested credentials appear on criminal marketplaces or in stealer logs. Early detection enables password resets before attackers use the stolen credentials.

Conclusion

Credential harvesting is the gateway to most modern cyberattacks. Attackers collect credentials through phishing and malware, then use them for account takeover and ransomware deployment.

The most effective defense combines prevention with detection. Technical controls like MFA and email security reduce successful harvesting. Credential monitoring catches what slips through by alerting you when your credentials appear on the dark web.

Start by understanding your current exposure. A dark web scan reveals which credentials attackers may already have. From there, you can prioritize password resets and strengthen defenses where they matter most.